1. Field of the Invention
Embodiments of the invention generally relate to a corrosion-resisting member for use in a treating apparatus for treating a substrate to be treated, and further relate to a ceramic member having excellent plasma resistance and particulate contamination prevention properties.
2. Description of the Related Art
Members disposed inside the chamber of a semiconductor or liquid-crystal production apparatus are located in a plasma treatment apparatus into which a fluorine- or chlorine-containing gas is introduced, and materials having high plasma resistance are desired. Many high-purity ceramic materials such as, e.g., high-purity aluminum oxide have been proposed as materials having high plasma resistance. In recent years, an yttria is attracting attention as a material having excellent plasma resistance. It has been pointed out that dusting occurs during etching due to member erosion and this dust adheres to the substrate being treated, resulting in particle contamination. Because of this, members having high plasma resistance and constituted of fine grains have been proposed, and materials reduced in grain boundary erosion and having a small impurity amount have been proposed.
In general, ceramics necessitate high temperature during firing for the production thereof and are hence produced through sintering, which is accompanied with grain growth. It is known that the ceramics yielded hence have a grain diameter lager than the particle diameter of the starting materials.
Ceramics constituted of large grains are known to be apt to suffer particle shedding.
It is also known that in case where a ceramic has voids in a portion to be exposed to a plasma, these voids serve as each of which is an origin of plasma erosion, resulting in poor plasma resistance.
Conventional techniques for producing a plasma resistant member include a method in which grain diameter is reduced to diminish particle shedding and a method in which a sintered body is produced so as to have a reduced porosity. An yttria is a material difficult to sinter and, hence, firing at a high temperature is necessary for obtaining a dense sintered body. Because of this, grain growth proceeds and this makes it impossible to obtain a sintered body constituted of grains with a small diameter. For example, JP-A-2006-21990 discloses that when a raw-material powder having an average particle diameter of 0.7 μm was used and firing was conducted at 1,700° C., then an yttria sintered body having an average grain diameter of 4 μm and a bulk density of 4.90 g/cm3 was obtained.
Furthermore, JP-A-2005-8482 discloses that when a raw-material powder having an average particle diameter of 1.2 μm was used, then firing at 1, 650° C. gave an yttria sintered body having an average grain diameter of 2 μm and a bulk density of 4.64 g/cm3, and firing at 1,710° C. gave an yttria sintered body having an average grain diameter of 12 μm and a bulk density of 4.90 g/cm3. It can be seen from these that for producing a dense yttria sintered body by an ordinary firing method, it is necessary to conduct firing at a temperature of 1,700° C. or higher.